With their wins, there are now five Senate races this fall that will feature only women as major party candidates.

Most recent election years have had just one or two states in which the nominees were both women. In 2012, the year the record was last set, there were three.

Senate races in which nominees were both women

As of Aug. 15

Five races

One race

1960

1986

1998

2018

As of Aug. 15

Five races

One race

1960

1986

1998

2018

As of Aug. 15

Five races

One race

1960

1986

1998

2018

If one of the two women running in the Republican primary for the Senate in Arizona later this month wins, as polls suggest, there would be six Senate races across the country in which a Democratic and a Republican woman are opposing each other.

Many of the candidates this year are newcomers, who span a wide range: A city councilwoman in Nebraska who has a family grocery store business; a Goldman Sachs-trained banker with an engineering degree from Stanford in New York; a former television news anchor; and state party chair in Washington.

Traditionally, the Senate has not been the most hospitable place for women. Only 23 women currently serve in the 100-person body — and that represents about half the number who have served in its history, 52.

Senate seats held by women

100 seats

75

50

Current breakdown

6 Republicans

17 Democrats

25

1917

2018

100 seats

75

Current breakdown

50

6 Republicans

17 Democrats

25

1917

2018

100 seats

75

50

Current breakdown

6 Republicans

17 Democrats

25

1917

2018

Note: Data shown for every other year.

Only 19 states currently have female representation in the Senate, and even fewer still are represented by two women, as shown in the map below.

Two female senators

One female senator

AK

ME

VT

NH

MA

WA

MT

ND

SD

MN

WI

MI

NY

CT

RI

PA

OR

ID

WY

NE

IA

IL

IN

OH

NJ

CA

NV

CO

WV

VA

MD

DE

UT

KS

MO

SC

AZ

NM

OK

AR

TN

KY

NC

TX

LA

MS

AL

GA

FL

HI

Two female senators

One female senator

AK

ME

VT

NH

MA

WA

MT

ND

SD

MN

WI

MI

NY

CT

RI

PA

OR

ID

WY

NE

IA

IL

IN

OH

NJ

CA

NV

UT

CO

KS

MO

WV

VA

MD

DE

SC

AZ

NM

OK

AR

TN

KY

NC

TX

LA

MS

AL

GA

FL

HI

Still, even with records falling as more women than ever before run, the number who actually make it to the Senate may remain flat — a case of one step forward, one step back.

“This is not going to turn around in one election cycle,” said Debbie Walsh, director of the Center for American Women and Politics at Rutgers University. “I think back to 1992, and we called that ‘The Year of the Woman,’” she added. That year was a success, she said, because the number of women elected to Congress doubled. “But it was still only 10 percent of the Congress.”

With more women running against other women, one replaces another. And that limits the overall change on the gender makeup of the Senate. But two female incumbents who are especially vulnerable this year — Heidi Heitkamp of North Dakota and Claire McCaskill of Missouri — are both Democrats running against men in states that President Trump won by double digits.

Senator Claire McCaskill (center) speaks during a news conference in the Capitol on July 19.Al Drago for The New York Times

And in Mississippi, the Republican Cindy Hyde-Smith, who was appointed to the Senate in April, is in a competitive three-way race against the Democrat Mike Espy and the Republican Chris McDaniel, to serve a full term in the seat vacated by Thad Cochran.

Their defeats would offset wins by women in states where they seem especially well positioned to win, like Arizona, Nevada and Tennessee.

As slow as gender parity is taking, the trajectory has been gradually upward. And it has been a much faster climb for women in the Democratic Party. The number of women who have won major party nominations for Senate this year hit 19, or about 29 percent of all primary winners, on Tuesday — another record. Six of those were Republican women (that was a record, too).

Primary winners in Senate races

100%

75

Male winners

50

As of Aug. 15

29%

25

Female winners

1994

2018

100%

75

Male winners

50

As of Aug. 15

29%

25

Female winners

1994

2018

100%

75

Male winners

50

As of Aug. 15

29%

25

Female winners

1994

2018

Note: Only includes major-party candidates who advanced to the general election. Data shown for every other year. Data for 2018 includes a special general election for a Minnesota Senate seat.

The record number of Republican women who have a shot at being elected to the Senate this year is a curious juxtaposition with the image of their party now that it is headed by President Trump, a man who has such a problematic history with women, and who faced repeated accusations of misconduct.

Ms. Housley, the Minnesota Republican nominee, said in an interview that the environment is certainly more difficult for conservative women this year, given all the activism on the left.

But Ms. Housley, a state senator from suburban Minneapolis, said that she sees herself as something of an ambassador to women who are on the fence about Mr. Trump and the Republican Party. “It's important for them to know that it’s O.K. for a woman to support President Trump,” she said. “Especially being a suburban woman myself, they look at you and go, ‘Wait a second. Here you are a strong woman, serving in politics, and you're still supporting Trump?’”

“They listen,” Ms. Housley added.

Jane Raybould, a Democrat on the Lincoln City Council who won a primary in May to challenge Senator Deb Fischer of Nebraska, recalled a story she said has been common as she campaigns across the state. Another woman approached her to tell her she had been to 19 protests in 23 months. “Really?” she remembered asking. “And she said, ‘I’ve never done anything like this in my entire life. I just could not sit on the sidelines anymore.’”

Sources: Center for American Women and Politics at Rutgers University; Associated Press; Dave Leip’s Atlas of U.S. Presidential Elections

Jeremy W. Peters reported from Milwaukee, and Denise Lu from New York.

Correction: Aug. 16, 2018

An earlier version of the graphic mislabeled the parties for the two United States Senate nominees in Nebraska. Incumbent Deb Fischer is a Republican, not a Democrat, and Jane Raybould is a Democrat, not a Republican.

Correction: Aug. 17, 2018

An earlier version of the graphic misspelled the given name of the incumbent in New York. She is Senator Kirsten Gillibrand, not Kristen.